Provisional Application No. 60/325,331, filed September 27,2001, which is incorporated in its entirety as a part hereof.

Field of the Invention This invention relates to the sputter deposition of epilayers using a plurality of magnetrons having different shapes.

Background of the Invention Radio frequency ("RF") magnetron sputtering techniques are widely used for the sputtering of thin films. In the case of sputtering thick films (i. e., films that are over one micrometer in thickness), however, alternating current ("AC") magnetron sputtering is advantageous since the deposition rate is higher.

In US 5,814, 195 and 6,365, 010, methods of sputtering are described using an AC power supply. In each instance, a plurality of magnetrons is used, such as cylindrical-shaped magnetrons, but the sputtering is only from the surface of the magnetrons.

It has now been found to be advantageous, in a sputtering process in which a plurality of magnetrons is employed, to utilize at least one magnetron that is shaped as a ring. The film deposited by such process will have reduced contamination.

Summary of the Invention One embodiment of this invention is an apparatus for film deposition having first and second magnetron targets within a sputtering chamber, wherein the second target is shaped as a ring, or a method for film deposition employing such apparatus.

A further embodiment of this invention is an apparatus for film deposition having first and second magnetron targets within a sputtering chamber, wherein the second target has an aperture that provides exterior and interior surfaces from which target material may be sputtered, or a method for film deposition employing such apparatus.

Another embodiment of this invention is, in a method of depositing a film by sputtering from a plurality of magnetron targets in a sputtering chamber, the step of periodically shifting the negative potential to a magnetron target that is shaped as a ring.

Yet another embodiment of this invention is, in a method of depositing a film by sputtering from a plurality of magnetron targets in a sputtering chamber, the step of periodically shifting the negative potential to a magnetron target that has an aperture that provides exterior and interior surfaces from which target material may be sputtered.

Brief Description of the Drawing Figure 1 is a diagram of components of a sputtering device.

Detailed Description of the Invention In this invention, a method and apparatus is provided for the epitaxial sputter deposition of a film on a substrate, particularly thick epilayers, at a high deposition rate. It is preferred to deposit the epitaxial films by using an AC magnetron sputtering technique.

A sputter epitaxy chamber for sputtering target materials, such as nonconductive materials, contains a plurality of magnetron sputtering targets as sources of sputter material. The targets may have different shapes, such as a planar shape and a ring shape. The preferred nature of ring-shaped magnetron is such that it possesses an aperture that provides exterior and interior surfaces from which target material may be sputtered. The ring-shaped magnetron need not be a perfect circle. It may formed in any shape that is suitable for the sputtering chamber, such as an essentially perfect circle, imperfectly circular, eliptical or polygonal, so long as the aperture is present. There is no limitation on the variety of dimensional sizes the ring-shaped magnetron may take along all three axes provided that it functions as intended for use as a magnetron.

An AC power supply is connected to first and second magnetron targets in a sputtering chamber, one of the magnetron targets being the ring-shaped magnetron. The ring-shaped magnetron may be disposed between another magnetron target, such as a planar, rectangular magnetron possessing no aperture, and the substrate. The ring-shaped magnetron may be constructed from the same material as another target or from just one or only some of the materials from which another target may be prepared. During the deposition process, first and second targets, one of which is the ring-shaped magnetron, act periodically as the cathode

and the anode. Sputtering from the magnetron target and ring-target together forms a film on the substrate.

A sputter epitaxy chamber for sputtering nonconductive materials includes two magnetron sputtering sources, at least one shaped as a ring and a substrate. Instead of having two planar, rectangular magnetron sputtering sources and connecting an AC power supply between them, we propose in this invention to have a plurality of magnetron sputtering sources, one of which is shaped as a ring. This magnetron is constructed from the same material as the other, or from one of the elements that make up the other target if it is a compound of multiple elements. During the deposition process, both targets act periodically as a cathode and an anode. The use of AC power causes the negative potential to periodically shift from one magnetron to another. When the negative potential shifts to the ring-shaped magnetron, material is sputtered from that target for deposition onto the substrate. The film on the substrate is thus sputtered from both first and second magnetrons, one of which is the ring-shaped magnetron. This reduces the deposition of contaminants on the film that might arise if AC is used with one pole run to a magnetron and one pole run to ground.

In Fig. 1, components of a sputter epitaxy chamber are shown, including a first magnetron sputtering source 2, a ring-shaped magnetron sputtering source 4, and a substrate 6. An AC power supply 8 is connected to the two magnetrons. The ring-shaped magnetron is disposed between the first target and the substrate. The ring-shaped magnetron is constructed from the same material as the first magnetron, or from just one of or some of the elements that make up the first target if the first target is a compound of multiple elements.

During the deposition process, the first target and the ring-shaped target act periodically as the cathode and the anode. The presence of the ring- shaped target helps to reduce contamination of the sputtered epitaxial film when the first magnetron target has positive voltage. Sputtering from both magnetron targets forms a film on the substrate. The ring-shaped magnetron target may have a cooling arrangement, such as a water jacket, since the deposition of thick films requires longer periods of sputtering.